Although frequently predicted to play critical roles in regulatory control, the nature and identity of functional noncoding sequences require comprehensive investigation. The inability to readily impute the functions of noncoding sequences, or the impact of variationtherein significantly hampers attempts to investigate potential associations between noncoding variation and disease susceptibility. The purpose of this grant is to systematically examine the regulatory potential of conserved noncoding sequences at a single human disease locus, RET. RET is a critical gene in the genesis and maintenance of multiple organ systems and a major susceptibility locus in multiple human disorders. This proposal has 3 major aims. First, we will use computational, in vitro and molecular analyses to identify S60 conserved noncoding regulatory sequences at RET, and begin to define critical sequences therein. Second, we will determine the biologic relevance of 3 identified regulatory sequences using plasmid-based transgenesis in mice to examine their in vivo regulatory function. Third, we will specifically examine the disease relevance of a single identified regulatory noncoding sequence. We will delete the selected sequence from a wild-type human BAG encompassing RET and compare the ability of wild-type and mutant transgenic mouse strains to complement the Ret null phenotype in mice. This proposal will yield insights into the nature of functional noncoding sequences at RET and in doing so provide a foundation for increasingly comprehensive investigation of putatively functional sequences at this and other disease loci. The central aim of this proposal is to begin to uncover the nature and identity of regulatory sequences through the systematic implementation of functional genetic analyses at the RET locus.